Idle drops when turning on lights (or electronics)
08-16-2008, 02:44 AM
#1
Drifting
Thread Starter
Idle drops when turning on lights (or electronics)
What would cause this? My battery voltage seems to be good. Alternator belt is tight.
My idle already seems to be a bit rough and lots of vibrations and shaking but goes away over 1000 rpm but at 950 rpm or lower it's very noticable at 11000 rpm and above no vibrations. Motor mounts are a year old but aftermarket from dealer 140 a piece.
I raised my idle a bit so it idles at 1000 rpm usually so I get less vibrations. However when I turn on my lights at night or even the heater fan etc the idle seems to drop from 1000 to 900 or so and the engine runs pretty rough (shaking) I have changed all my vacuum lines, cap rotor, wires, plugs so i'm not sure why it's idling bad and rought. I also replaced the idle control valve and it works (vibrates).
i'm guessing that a drop in voltage when i turn on the lights or electronics is causing a rought idle so what would be the most likely cause of this?
thanks
My idle already seems to be a bit rough and lots of vibrations and shaking but goes away over 1000 rpm but at 950 rpm or lower it's very noticable at 11000 rpm and above no vibrations. Motor mounts are a year old but aftermarket from dealer 140 a piece.
I raised my idle a bit so it idles at 1000 rpm usually so I get less vibrations. However when I turn on my lights at night or even the heater fan etc the idle seems to drop from 1000 to 900 or so and the engine runs pretty rough (shaking) I have changed all my vacuum lines, cap rotor, wires, plugs so i'm not sure why it's idling bad and rought. I also replaced the idle control valve and it works (vibrates).
i'm guessing that a drop in voltage when i turn on the lights or electronics is causing a rought idle so what would be the most likely cause of this?
thanks
08-16-2008, 03:06 AM
#2
Three Wheelin'
hmm... i don't know for sure but i'd check all the earth cables (battery, engine, etc) are in good condition and are making good contacts.
08-16-2008, 07:57 AM
#3
Rennlist Member
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Do you have a volt meter? Check the voltage between the + and - battery posts with the car running. It should be above 13.5V. If not, your alternator (more likely the voltage regulator) is not charging.
As far as the engine vibration goes you could still have a failed motor mount. I had a fairly new aftermarket mount fail. Measure the distance between the bottom of the rubber portion to the top on both sides. If one side is lower then you found the vibration problem. Usually the exhaust side fails first. Get it replaced soon because a vibrating engine could cause all sorts of problems like cracked fuel rails, etc;.
As far as the engine vibration goes you could still have a failed motor mount. I had a fairly new aftermarket mount fail. Measure the distance between the bottom of the rubber portion to the top on both sides. If one side is lower then you found the vibration problem. Usually the exhaust side fails first. Get it replaced soon because a vibrating engine could cause all sorts of problems like cracked fuel rails, etc;.
08-17-2008, 05:29 PM
#4
Rennlist Member
It sounds like it is normal, IMO. The devices you are turning on require more power, which then puts a higher load on the alternator to supply this higher power. The higher load on the alternator requires more power from the engine to turn, but because these cars don't have a PCM controlled idle like newer cars, the engine does not increase the amount of air going into the engine. Since the throttle isn't increased to offset the increased load, the rpm's drop.
Same idea as turning on the a/c at idle, or cranking the steering and putting a high load on the powersteering pump at idle.
Same idea as turning on the a/c at idle, or cranking the steering and putting a high load on the powersteering pump at idle.
